Mammary glands exhibit molecular laterality and undergo left–right asymmetric ductal epithelial growth in MMTV-cNeu mice*

Significant left–right (L–R) differences in tumor incidence and disease outcome occur for cancers of paired organs, including the breasts; however, the basis for this laterality is unknown. Here, we show that despite their morphologic symmetry, left versus right mammary glands in wild-type mice have baseline differences in gene expression that are L–R independently regulated during pubertal development, including genes that regulate luminal …